PythonApt: CacheProgressHelper now ensures that the percentage reported is always higher than the last percentage reported (fixes progressbar moving backwards problem).
Gtk Frontend: Removed comment about DBUS being broken, this has been fixed.

Things are starting to work again.
DistSpecific base added, different update category detection for
Debian and Ubuntu implemented.
Gtk UI now shows packages in correct categories and displays the package
description in the details.
Dbus is working again.

Updated python-apt backend to reflect latest changes to lp:python-apt.
Gtk frontend does not call sys.exit anymore, but uses gtk.main_quit(), which
makes sure control is passed back to the Application instance and cleanup
can be done.

Logging should be initialized as early as possible in Application.py.
Added unprivileged invocation handler method definition to Frontend.
Added implementation of unprivileged invocation handler to Gtk Frontend.
Automatically detect if code is executed in-tree and set DATA_DIR in Gtk Frontend accordingly.
ListProgressHelper is now included in API documentation.